In electro-photoelectric type image forming apparatus such as a copier, a printer, etc., a fixing unit which clamps and conveys a sheet of paper transferred a toner image formed on a photosensitive unit by fixing rollers having a heat source and heats, presses and fixes the toner image is broadly used. Further, as a result of diversification of image forming apparatus in recent years, an image forming apparatus that is further small in size and light in weight is demanded. And it is tried to make component units themselves of an image forming apparatus small and the conveying passage of sheets of paper short. In order to make the paper conveying passage short, an apparatus to make the transfer and fixing of toner images while conveying sheets of paper supplied from a paper supply unit at the lower side in the vertical direction has been provided.
However, in a small sized apparatus that vertically conveys sheets of paper, a space for vertically conveying sheets of paper at the time of the transfer and fixing is limited and the temperature rise around as fixing unit is unavoidable.
The temperature rise in the vicinity of the fixing unit may affect the charging characteristics of a photo-conductor or the developing characteristics of toner and lower the image quality. In the Japanese Patent Application No. 2002-189380, a configuration of an image forming apparatus to cool the inside of the main body by leading heat generated around a fixing unit or a photosensitive unit to the exhaust port through the clearance of them by a fan for exhausting radiant heat around the fixing unit is disclosed.
However, it is not possible to exhaust the radiant heat generated by a fixing unit directly to the outside of the main body of an image forming apparatus by a fan only as in a conventional apparatus. Furthermore, because a space to separate the photosensitive unit and the fixing unit is narrow, the radiant heat of the fixing unit turns around the photosensitive unit and may heat peripheral units and so. The units around the photosensitive unit may raise their temperatures. The image quality may be lowered for change in the characteristics, when the temperature of the photosensitive unit rises. Or, recovered toner may become inadequate for the recycle for deterioration of the toner characteristics, when the temperature of the cleaner rises.
Therefore, in a small sized image forming apparatus with a limited space for separating a photosensitive unit and a fixing unit, an image forming apparatus and a process cartridge, capable of efficiently exhausting radiant heat of a fixing unit directly to the outside of the apparatus, preventing temperature rise in the vicinity of the photosensitive unit and improving image quality, extending the life of toner by preventing deterioration of its characteristics resulting from the temperature rise, and enabling recycle use of recovered toner are demanded.